An apparatus for calibrating or sizing a tubular foil balloon in the blowing of a thermoplastic foil can comprise a pair of iris-type aperture calibrating devices or a segment-type calibrating device.
The iris aperture calibrating devices are spaced from each other and each have a plurality of iris aperture leaves which are movable and adjustable by a positioning ring which is mounted in an iris aperture housing.
The segment calibrating device has a plurality of curved segments which make up a polygonal structure, which are connected to a plurality of supporting or carrying members and which are adjustable with the aid of an adjusting lever system.
The iris aperture leaves are generally sickle or crescent shaped. The iris aperture calibrating devices are commercial calibrating devices which operate according to the iris aperture principle (see for example Meyers Encyclopedia Dictionary, Volume 4, Page 334 (1972)--Meyers enzyklopadisches Lexikon 1972, Band 4, Seite 334).
The edges of the iris-type aperture leaves, which are usually sickle shaped, together make up a curve which approximates a circle. The approximation is all the more exact the greater the number of iris-type aperture leaves and also depends on the aperture opening. The aperture opening of the iris-type aperture calibrating devices can be adjusted by hand or by an adjusting motor.
These known calibrating apparatuses are provided independently of one another. They have different design purposes, and, depending on need, one can use either the iris-type aperture calibrating device or the segment-type calibrating device.
Thus, according to the plastic material of the foil it has been necessary heretofore to provide either an iris-type aperture calibrating device or a segment-type calibrating device.
In a conventional manufacturing unit for tubular balloons the segment-type calibrating device is customarily located beneath the iris-type aperture calibrating devices. It operates with an adjusting lever system in which the components are constructed for their part like scissors levers. This adjusting level system is connected to a single drive (German Patent Document No. DE-OS 31 17 806).